^^^^
Not wanting to alarm anyone with my DV suggestion - It's only a total guess as a possibility. If you had a DV leak I would expect a power 'leak' and especially a loss under hard throttle.
The sound might even be on my car too. As bacillus points out, there is a myriad of noises and my squeeeeek might be lost amongst the glorious Grrrrrrrr! from my engine mounts, usual Twintake sounds, Milltek exhaust, and occasional whine (which I enjoy) from the gears/Quaife.